Brake controlling device

ABSTRACT

The present invention relates to a device for controlling the brake in winches which are driven by a hydraulic motor and have a brake which is engaged when not actuated and arranged to disengage when a pressure medium is delivered to a hydraulic cylinder connected to the brake. The invention is chiefly characterized by a brake controlling unit which is connected to the high pressure side of the motor and is arranged to regulate the supply of pressure medium to the brake&#39;&#39;s hydraulic cylinder, depending on the size of the motor load, so that during a lifting operation, the brake releases only after the pressure on the motor&#39;&#39;s high pressure side substantially corresponds to the pressure required to balance the load. In addition, means are provided to release the brake at a pressure during lowering of the load, independent of the size of the load.

United States Patent [191 Edlund et al.

[451 Dec. 25,1973

[ BRAKE CONTROLLING DEVICE [73] Assignee: AB Hagglund & Soner,

Ornskoldsvik, Sweden [22] Filed: Jan. 24, 1972 [21] Appl. No.: 220,133

[30] Foreign Application Priority Data 4/1948 Canada 254/173 Primary Examiner-Evon C. Blunk Assistant Examiner-James W. Miller Attorney-Cushman, Darby & Cushman [57] ABSTRACT The present invention relates to a device for controlling the brake in winches which are driven by a hydraulic motor and have a brake which is engaged when not actuated and arranged to disengage when a pressure medium is delivered to a hydraulic cylinder connected to the brake. The invention is chiefly characterized by a brake controlling unit which is connected to the high pressure side of the motor and is arranged to regulate the supply of pressure medium to the brakes hydraulic cylinder, depending on the size of the motor load, so that during a lifting operation, the brake releases only after the pressure on the motors high pressure side substantially corresponds to the pressure required to balance the load. In addition, means are provided to release the brake at a pressure during lowering of the load, independent of the size of the load.

2 Claims, 2 Drawing Figures PATENTEU DEC 2 5 i975 PRIOR ART BRAKE CONTROLLING DEVICE The present invention relates to a device for controlling the brake in winches which are driven by a hydraulic motor and have a brake which is engaged when not actuated and arranged to disengage when a pressure medium is delivered to a hydraulic cylinder connected to the brake.

ln most of the applications of winches driven by a hydraulic motor, some form of combined parking and emergency brake is required. The construction of the brake varies, but the most common embodiment has a strap brake that is actuated by a spring-loaded hydraulic cylinder. Common to all solutions to the problem is that the brake is automatically engaged and brakes the load when the pressure in the motors hydraulic system ceases. When the pressure in the hydrualic system ceases, the outer suspending load tends to drive the motor, thus making it work as a pump. Two types of leakage occur then in the motor viz. an outer and an inner leakage. The outer leakage runs via the motors drainage pipe back to the tank while the inner leakage occurs between the high and the low connections of the motor.

With known brake arrangements of the above known type, pressure medium is usually supplied to the brake cylinder directly from the feeder of the pump; the brakes releasing pressure lies in the magnitude of 30 kp/cm depending on size of the motor. A pressure of this magnitude ensures that the brake disengages before the motor is started without a load. However, such an arrangement has considerable drawbacks when the motor is started with a suspended load, and particularly during slow lifting of a normal load, a hydraulic pressure on the high pressure side of the motor is required in the magnitude of 150 200 kp/cm. As a result, whenthe hand valve of the motor is moved to the lifting position, the brake will disengage before a hydraulic pressure has been attained which is sufficient to balance the load and, respectively, drive the motor for lifting operations. With insignificant action on the hand valve, the situation may arise whereby the building up of sufficient pressure is impossible. However, the pressure is sufficient to release the brake which means that the load will containuously sink despite the fact that the control lever is actually in the lift position.

The purpose of the present invention is to produce a device for brake control whereby the above mentioned drawbacks are totally eliminated. This is achieved according to the invention by means of a brake control unit connected to the high pressure side of the motor, which unit is arranged to regulate the supply of pressure medium to the brakes hydraulic cylinder, depending on the size of the motor load, so that during lifting the brake releases only when the pressure on the high pressure side of the motor substantially corresponds to the pressure required to balance the load. Means are provided to release the brake during lowering at a pressure independent of the size of the load.

According to a preferred embodiment of the invention, the brake control unit comprises a hydraulic pressure accumulator, which is connected with the motors high pressure connection over a non-return valve opening away from the motor, and a spring-loaded control valve which is arranged in a pressure medium supply line to the brake cylinder. One side, the control valve communicates with the accumulator and is actuated by the pressure in the accumulator against the effect of the spring force towards a first position at whichthe pressure medium supply to the brake cylinder is interrupted; on the other side, the control valve communicates with the motors high pressure line and is actuated by the pressure in said line towards a second position where it is open to allow free passage of pressure medium to the brake cylinder. During lifting, the accumulator is charged to the pressure in the system, which depends on the size of the load, required for the lifting operation. If the motor is then stopped so that the hydraulic system has no pressure and the brake engages, due to the non-return valve connected in front of the accumulator the latter will maintain the pressure prevailing during lifting and hold the control valve closed with a force corresponding to said pressure. Thus, the accumulator serves as a memory which stores information concerning the pressure required for lifting the load. When the lifting operation is resumed, the control valve will open the connection with the brake when the pressure on the control valves opposite side, connected to the feeder of the motor on the high pressure side, exceeds the pressure in the accumulator minus the pressure corresponding to the force of the spring built in to said control valve. The brake will hereby release only when the pressure on the high pressure side of the motor is sufficient to balance the load so that there will be no risk of the load sinking first.

The means which cause the brakes to release independent of the size of the load during the lowering operation consist preferably of a reverse valve arranged in the pressure medium line between the control valve and the brake cylinder. This reverse valve communicates with the low pressure side of the motor and a short-circuit valve coupled over the accumulator and the non-return valve. The short-circuit valve is arranged to be controlled by the pressure on the low pressure side of the motor. During lowering, the pressure medium is delivered via the reverse valve to the brake cylinder from the motors low pressure side, independent of the pressure in the accumulator which is shortcircuited by the short-circuit valve. Thus, e.g., when the load is lowered to the ground, the accumulator is discharged since the motor is unloaded when the next lifting movement begins.

The control device according to the invention is now described in detail with reference to an embodiment shown on the accompanying drawing. FIG. 1 is a wiring diagram of a control system for a hydraulic winch motor with conventionally regulated brakes. FIG. 2 is a wiring diagram corresponding to the system in FIG. 1, but with a brake control device according to the invention.

In FIG. 1, the hydraulic system is fed oil by a pump 1 from a tank 2 to a hand valve, indicated by 3. This valve communicates via a line 4 with the low pressure side 5 of a hydraulic winch motor 6, and via a line 7 with the high pressure side 8 of said motor 6. Coupled into the high pressure line 7 is a back-pressure valve 9 which communicates with the low pressure line 4 and is controlled by the pressure in said line 4. There is a filter 10 in the return line from the hand valve 3 to the tank 2.

To prevent the motor 6 from being operated as a pump by a suspended load when pressure in the system ceases, e.g., when the hand valve 3 is in the neutral position shown in the figure, a brake 11 is provided. The

brake, which is preferably a strap brake, is of the type which, when not actuated, is kept engagedby means of a powerful spring and is made to'release by the supply of oil to a hydraulic cylinder which is connected to the brake and acts against the force of the spring. In the fig ure, the spring and the brake are built together as one unit 12 which is fed oil via a line 13 connected with the feeder of the pump 1. I

When the hand valve 3 is in neutral position, as shown in FIG. 1, oil is fed from the tank 2 to the valve 3 and from there back to the tank via the filter 10. There is no, or insignificant pressure in the line 13. Therefore, the brake 11 is kept engaged. If thehand valve 3 is moved to the lifting position (its right hand position), the pressure in the pumps feeder rises simultaneously with pressure in the brake line 13. When a pressure of IO 30 kp/cm depending on the size of the motor has been reached in the line 13, the brake cylinder 12 releases the brake 11. However, this pressure is not sufficient to hold a suspended normal load where, in general, a pressure of 150 200 kp/cm is required. Before a pressure of this magnitude has been reached on the high pressure side 8 of the motor, said motor will be forced backwards by the load like a pump at a speed proportional with the inner and outer leakage of the motor.

In FIG. 2, the brake line 13 of FIG. 1 has been replaced by a brake controlling device according to the invention in order to remove the above mentioned drawbacks. Otherwise the two figures are identical; thus corresponding components have the same reference numerals.

The brake controlling device comprises a hydraulic pressure accumulator 14 which is connected directly to the high pressure side 8 of the motor 6 over a nonreturn valve 15 opening away from the motor 6. The accumulator is also connected to one side of a pilotcontrolled two-position valve 16 so that the pressure in the accumulator actuates one side of a pilot piston displaceable in the valve 16 and tends to move the piston to the right in the figure in response to the effect of a spring 17. Thus the valve 16 assumes the position I indicated in the figure. The opposite side of the valve 16 communicates via a line 18 with the high pressure line 7 of the motor 6 so that the pressure in the line 18, together with the spring 17, strives to displace the pilot piston to the left towards a valve position II.

The valve 16 is arranged between a line 19, which is connected to the high pressure line 7 via the line 18, and a line which, via a reverse valve 21, is connected to the brake cylinder 12. In position [I shown in the figure, connection is made between the lines 19 and 20 so that pressure medium can flow freely from the high pressure line 7 via the valve 16 and the valve 21 to the brake cylinder 12 to release the brake 11. In position I, the line 19 is closed and the line 20 communicates with the tank 2 so that the brake cylinder is drained for application of the brake.

The above described system relates to the high pressure side of the motor 6. On the low pressure side, there is a line 22 which, via a reverse valve 21, connects the brake cylinder 12 with the motors low pressure line 4. In addition, a short-circuit valve 23 is coupled over the non-return valve 15 and the accumulator 14 to shortcircuit the non-return valve and discharge the accumulator 14. The valve 23 communicates with the low pres sure line 4 and is controlled by the pressure in said line The function of the device according to the invention will now be described the starting point being when the winch is to lift a load resting on the ground. The hand valve 3 is in the neutral position shown in FIG. 2; the brakes are engaged and the accumulator 14 is assumed to be discharged. When the valve 3 is moved to the lifting position, oil is fed to the high pressure side of the motor 6 over the line 7 and simultaneously over the lines 18 and 19 to the valve 16. Since the pressure accumulator 14 is discharged, the valve 16 may be arranged so that the force of the spring 17 will be sufficient to keep said valve 16 open so that the oil can flow freely from the high pressure side via the lines 19 and 20 to the brake cylinder 12. The brake 11 thus disengages even at a'low pressure. This is advantageous since the motor first operates with low pressure only to take up the slack in the line before the load is lifted from the ground.

When the load is lifted, the pressure on the high pressure side 8 of the motor 6 increases to 200 kplcm Corresponding pressure will prevail in the accumulator 14 which is thus kept continuously charged to a pressure equal to the pressure required to lift the load. Corresponding pressure also prevails on both sides of the pilot piston, on one side by the influence of the pressure in the accumulator l4, and on the other side by the pressure in the line 18 which is equal to the pressure on the high pressure side 8 of the motor. The valve 16 is therefore kept in position II in open position by the spring 17 so that the brake is kept disengaged.

If the hand valve is moved to the neutral position so that the motor stops and the load is suspended freely, the pressure in the line 18 sinks. However, the pressure in the accumulator 14 remains the same as during the lifting because of the non-return valve 15 which prevents discharging of the accumulator. The pressure in the accumulator then acts to displace the pilot piston to the right so that the valve 16 assumes the position indicated by I. In this position, the line 19 is closed and the line 20 is connected to the tank. Thus the brake cylinder 12 is drained and the brake is applied.

When the suspended load is to be raised again by moving the valve 3 to the lifting position the connection between the lines 19 and 20 will be broken thus preventing the supply of the pressure medium to the brake cylinder until the pressure on the motors high pressure side, and thereby even in the line 18, has reached a pressure equal to the pressure in the accumulator 14 minus the pressure corresponding to the force of the spring 17. As soon as this pressure is exceeded, the valve 16 will open the supply line to the brake which thus releases only at a pressure sufficient to balance the load.

If, however, the load is to be lowered by moving the valve 3 to the left position in the figure it is obviously not necessary to attain a pressure on the high pressure side beforethe brake ll releases. During the lowering operation, the brake cylinder will instead be supplied with pressure medium over a line 22 which is connected with the low pressure line 4 of the motor and communicates, viathe reverse valve 21, with the brake cylinder 12. Since the line 20 is coupled to the tank over the valve 16, and is thus pressureless, the pressure in the line 22 will move the ball-shaped valve body in the valve 21 to the right in the figure and open the connection between the line 22 and the brake cylinder 12 at the same time as the line 20 is blocked. Thus, the brake is already released at a low pressure which is independent of the size of the load.

When the load is lowered, the pressure on the motors high pressure side 8 is determined by the backpressure valve 9 connected with the low pressure side 5. This pressure will now depend on the size of the load. This means that even during lowering the accumulator 14 will be kept charged with a pressure dependent on the size of the load so that, during a subsequent lifting, the brake releases only once the pressure on the high pressure side 8 of the motor 6 is sufficient to balance the load. However, during the actual lowering of the load, the non-return valve is short-circuited by the short-circuit valve 23, which is controlled from the low pressure side, so that the accumulator 14 can be discharged when the load is lowered to the ground since the winch starts without the load at the beginning of the next lifting movement. However, this applies only when the load is lowered to the ground. If the motor stops with the load freely suspended after lowering, what was previously described applies since the valve 23 immediately opens at the drop of pressure on the low pressure side 5 of the motor. Thus the accumulator remains charged by the pressure corresponding to the pressure required to balance the load.

What we claim is:

1. Device for brake control in winches driven by a hydraulic motor, said winches having a brake which is engaged when not actuated, said brake being arranged to release by means of the delivery of pressure medium to a hydraulic cylinder connected to the brake, characterize by a brake controlling unit which is connected to the high pressure side of the motor and is arranged to regulate the supply of pressure medium to the brakes hydraulic cylinder, depending on the size of the motor load, so that during a lifting operation, the brake releases only after the pressure on the motors high pressure side substantially corresponds to the pressure required to balance the load, means being arranged in order to release the brake at a pressure, during lowering of the load, independent of the size of the load, said brake control unit comprises a hydraulic pressure accmmulator, which is connected with the motors high pressure line over a non-return valve that opens away from said motor, and a spring-loaded control valve which is arranged in a pressure medium supply line to the brake cylinder and which, on the one side, communicates with the accumulator and is actuated 'by the pressure in said accumulator against the effect of the force of the spring towards a first position, at which pressure medium delivery to the brake cylinder is interrupted and, on the other side, communicates with the motors high pressure line and is actuated by the pressure in same towards a'second position, at which the control valve is open to allow free passage of the pressure medium to the brake cylinder.

2. Device according to claim 1, characterized in that the pressure medium line, which is connected between the control valve and the brake cylinder, communicates via a reverse valve with the low pressure side of the motor, and that a short-circuit valve is coupled over the non-return valve and the pressure accumulator, said short-circuit valve being arranged to be controlled by the pressure on the motors low pressure side. 

1. Device for brake control in winches driven by a hydraulic motor, said winches having a brake which is engaged when not actuated, said brake being arranged to release by means of the delivery of pressure medium to a hydraulic cylinder connected to the brake, characterize by a brake controlling unit which is connected to the high pressure side of the motor and is arranged to regulate the supply of pressure medium to the brake''s hydraulic cylinder, depending on the size of the motor load, so that during a lifting operation, the brake releases only after the pressure on the motor''s high pressure side substantially corresponds to the pressure required to balance the load, means being arranged in order to release the brake at a pressure, during lowering of the load, independent of the size of the load, said brake control unit comprises a hydraulic pressure accmmulator, which is connected with the motor''s high pressure line over a non-return valve that opens away from said motor, and a spring-loaded control valve which is arranged in a pressure medium supply line to the brake cylinder and which, on the one side, communicates with the accumulator and is actuated by the pressure in said accumulator against the effect of the force of the spring towards a first position, at which pressure medium delivery to the brake cylinder is interrupted and, on the other side, communicates with the motor''s high pressure line and is actuated by the pressure in same towards a second position, at which the control valve is open to allow free passage of the pressure medium to the brake cylinder.
 2. Device according to claim 1, characterized in that the pressure medium line, which is connected between the control valve and the brake cylinder, communicates via a reverse valve with the low pressure side of the motor, and that a short-circuit valve is coupled over the non-return valve and the pressure accumulator, said short-circuit valve being arranged to be controlled by the pressure on the motor''s low pressure side. 